Chain operating systems for window blinds are known in the art. They generally include a sprocket or drive wheel for driving a driven blind member such as a drive shaft, a ball chain operatively engaging the sprocket wheel, a cover on the sprocket wheel and a chain stopper on the ball chain. In these systems, the sprocket wheel is drivingly connected to a driven member of a blind. For example, the blind may be a roller blind or a vertical venetian blind. A sprocket wheel can also drive other blinds, such as a horizontal venetian blind or a roman shade. The driven member can be a conventional drive shaft of a roller blind, a central control shaft of a roman shade, a lift or tilt shaft of a horizontal venetian blind or a traverse or tilt shaft of a vertical venetian blind, or the like.
The ball chain, in such systems, comprises a plurality of spaced apart balls. The ball chain is looped over the sprocket wheel to operatively engage it, so that first and second depending portions of the ball chain are on either side of the sprocket wheel. By pulling one of the depending portions of the ball chain, the sprocket wheel is rotated in either a clockwise or counter-clockwise direction, and the driven shaft also is rotated. This results in a roller blind being rolled up or unrolled, a venetian blind being tilted or lifted or lowered, a vertical venetian blind being traversed or tilted or a roman shade being lifted or towered.
The sprocket wheel, in such systems, is typically hidden with a cover. The cover generally is over at least the part of the sprocket wheel where the ball chain is looped over it, but open top covers are also known (e.g., U.S. Pat. No. 2,577,046). The cover is open at the bottom for passage of the opposite depending portions of the ball chain. The cover acts as a guiding means to guide the ball chain into engagement with the sprocket wheel and prevent the ball chain from disengaging from the sprocket wheel.
In such systems, ball chains have been provided with one or more separate members which act as chain stoppers. The stoppers are adapted to block movement of the ball chains into the mechanism, thus stopping the rotation of the sprocket wheels and operating movement of the blinds. They have also been used to prevent ball chain from being pulled further than necessary for performing desired operating movements of the blinds, for example, for preventing farther than a maximum tilt of a venetian blind or preventing a roller blind from being rolled-up too far whereby its bottom would collide against its roller or its housing.
The chain stoppers are often larger than the cross-section of the balls or entrance into the clutch covers. These stoppers thus block the ball chains at the bottom of the sprocket covers and prevent the ball chains from being further pulled over their sprocket wheels.
Beaded (ball) chains or cords are thus utilized in roller shades, curtains and blinds for opening or closing the roller shades, curtains or blinds in a horizontal or vertical direction. Existing beaded chains utilize a continuous headed chain in which all of the beads are of uniform size except one or two stopper beads which are of larger size. Such beaded chains introduce a purely “by chance” event when rotating the chains as there is no way for an operator to know which chain direction is going to produce the desired result. In some situations, a person desiring to open the roller shade, curtains or blinds will pull on a side of a chain/cord only to jam or disengage from the clutch mechanism. For example, excessive forces applied to the ball chain can cause the larger chain stopper to crash into the clutch housing and disengage the ball chain or cause other damage to components of the clutch.
In addition to frustrating the operator, pulling the beaded chain in the undesired direction introduces unnecessary wear and tear on the mechanisms of the roller shades, curtain or blinds. For example, if a roller shade is fully opened, a hard tug on the chain stresses the chain because the roller shade does not move in response to the downward pulling force. A strong tug on the chain when the roller shade is at full extension, either opened or closed, has the potential of snapping the chain, damaging the housing or clutch, or worse, pulling an entire assembly off of a wall. Similarly, a tug on the incorrect side of the beaded chain, will cause the beaded chain or the gearing to slip which, over an extended time, will degrade the rotational mechanisms of the blinds.
A beaded chain of the prior art does not provide an operator with the opportunity to learn which chain side to pull because the beaded chain tends to hang in such a manner that the sides of the chain are indistinguishable. For example, the chain sides often are touching or are wound around each other, and may not be in predictable locations, e.g. to the front or to the back, due to interference with the blinds, furniture, or the window sill. Further, the typical operator does not have the patience to scrutinize the chain and sprocket (not shown) to determine which side to pull.